#include<bits/stdc++.h>
#define MULT_TEST 1
#define int long long
using namespace std;
typedef array<int, 2> pii;
typedef unsigned long long ull;
const int INF = 0x3f3f3f3f;
const int MOD = 998244353;
inline int read() {
    int w = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if(ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        w = (w << 1) + (w << 3) + ch - 48;
        ch = getchar();
    }
    return w * f;
}
inline void Solve() {
    int n, ans = 0;
    n = read();
    ans = read();
    for (int i = 2; i <= n; i++) {
        int a = read();
        ans = ((ans + a) % MOD + ans * a % MOD) % MOD;
    }
    printf("%lld\n", ans);
}
signed main() {
    int T = 1;
#if MULT_TEST
    T = read();
#endif 
    while (T--) Solve();
    return 0;
}